The present invention relates, in general, to tissue fastening devices and, in particular, to a new and useful wound closure device, such as a skin stapler, that allows for the multi-directional release of a staple from the device upon firing while utilizing a novel rack and pinion staple feed mechanism.
It is well established in the prior art that there are many devices that exist which utilize staples for fastening tissue. Many of these existing or known devices are directed toward closing a wound, fastening a skin incision, curing a defect in tissue or fastening a prosthetic to tissue for repairing a defect or the like.
In particular, there are a number of known prior art skin staplers that contain a multiplicity of staples and are used for closing wounds or incisions in the skin. These skin staplers are usually multi-fire instruments meaning that they contain and fire a plurality of staples. These instruments are designed to be disposable and used for a single patient only.
One known prior art skin stapler is disclosed in U.S. Pat. Nos. 4,391,402; 4,406,392 and 4,591,086 (Campbell et al.). Similar to many other known skin staplers, the stapler disclosed in the above-identified patents utilizes an L-shaped anvil. The L-shaped anvil configuration comprises an elongated leg portion and a small leg portion that is orthogonal or parallel to the elongated leg portion for providing a staple forming surface thereon. Accordingly, a former or driver is used to move parallel to the elongated leg portion in order to form a staple around the small leg portion of the anvil. In conjunction with the driver and anvil configuration and orientation, a leaf spring, which is a unitary part of the staple track, is utilized for retaining the staple stack away from the staple being formed, e.g. the distal-most staple, on the small leg portion of the anvil in order to prevent the staple stack from interfering with the forming of the distal-most staple.
Other known skin staplers are disclosed in U.S. Pat. No. 3,643,851 (Green et al.) and U.S. Pat. No. 4,127,227 (Green). Similar to the prior art devices described above, these skin staplers utilize a similar anvil having a substantially L-shaped configuration. Additionally, the driver for these stapling instruments is advanced parallel to the elongated leg portion of the anvil. Additionally, a spring ejector is located adjacent the anvil for engaging the formed staple at the crown of the staple in order to lift the staple off of the anvil by its crown after firing.
In addition to the skin staplers identified above, there are other known skin staplers which also utilize a spring ejector for ensuring that the formed staple is moved away from the anvil of the instrument. These devices are identified as follows: the PRECISE PGX.TM., manufactured and sold by 3M Healthcare, St. Paul, Minn.; the Davis-Geck APPOSE ULC.TM., manufactured and sold by American Cyanamid Company, Danbury, Conn.; VISISTAT RH.TM., manufactured and sold by Edward Weck and Company, Inc., Research Triangle Park, N.C.; and the Auto Suture (Cricket.TM., Royal.TM., Signet.TM., Concorde.TM., Elite.TM. and Multi-fire Premium.TM.) skin stapler products, manufactured and sold by United States Surgical Corporation, Norwalk, Conn. All of these skin stapler products are available in the market and utilize a similar driver and anvil configuration such as disclosed above. These devices all utilize a driver that moves substantially parallel to the elongated leg portion of the anvil in order to form a staple across the surface of the small leg portion of the anvil. Furthermore, in all of these skin stapler devices, the staple is moved away from the anvil of the instrument through the use of a spring ejector which engages the staple at the far corners of the staple crown, i.e. at the juncture of the upper most portion of the staple leg and the corner of the staple crown. Accordingly, the staple is dislodged from the surface of the anvil by using the spring ejector to force the staple off of the anvil by its crown.
One skin stapler that utilizes a spring ejector or kick-off spring to release the staple from the skin stapler is the PROXIMATE PLUST.TM. Skin Stapler manufactured by Ethicon Endo-Surgery, Inc., Cincinnati, Ohio. This skin stapler utilizes a novel kick-off spring that has a tip which cams against the legs of the staple in order to eject the staple off of and away from the anvil of the stapler. This skin stapler is embodied in pending U.S. patent application Ser. No. 08/815,811 (Applicant's Docket No. END-378) filed on Mar. 12, 1997 which is incorporated herein by reference.
Additionally, the PROXIMATE PLUS.TM. Skin Stapler also utilizes a spring biased staple feed mechanism in order to feed each staple from the staple stack to the anvil of the stapler. This spring biased staple feed mechanism utilizes a spring coil and is embodied in U.S. Pat. No. 4,179,057 (Becht et al.) which is also incorporated herein by reference as well as embodied in the pending application identified above.
Since this staple feed mechanism is a spring coil, it is required to meet a minimum spring force threshold so that the staples can be fed to the anvil of the instrument. Accordingly, each spring coil is tested prior to instrument assembly to ensure that the spring force threshold is met.
The present invention is directed to a staple feed mechanism that eliminates the spring coil and the pre-assembly testing outlined above.